Percussive tool



Oct. 27, 1931. w. A. SMITH. sR.. ET AL 1,829,246

PERCUS S IVE TOOL THE/Y1 A TTORNEY- Filed July 27, 1929 Patented Oct. 27, 1931 UNITED STATES PATENT OFFICE WILLIAM A, SMITH, 83., 0F EAS'TON, PENNSYLVANIA, AND WILLIAM A. SMITH, J 3., O]?

PHILLIPSBURG, NEW JERSEY, ASSIGNORS TO INGERSOLL-RALND COMPANY, OF JER- SEY CITY, NEW JERSEY, A CORPORATION OF NEW JERSEY PERCUSSIVE TOOL Application filed July 27, 1929.

This invention relates to percussive tools, and more particularly to percussive tools employing differential hammer pistons for actuating the working implement and in which the hammer piston or a portion thereof serves to control the distribution of the pressure fluid to the piston chamber.

' One object of the invention is to obtain a maximum amount of work from the tool with a minimum expenditure of pressure fluid.

Another object is to obtain a rapid action of the percussive element of the tool, and still another object is to render the tool free from objectionable shocks and vibration.

Other objects will be in part obvious and in part pointed out hereinafter.

In the drawings illustrating one form which the invention may-assume in practice,

Figure 1 is a sectional elevation of a percussive tool constructed in accordance with the practice of the invention and showing the piston in a position to begin its forward stroke, and

' Figure 2 is a view similar to Figure 1 showing the piston aboutto begin its rearward stroke. I

' Referring more particularly to the drawings, A representsthe cylinder of a percussive tool and B a piston chamber therein comprising in this instance an enlarged bore O and areduced or smaller bore D. A closure is provided for the front end of the piston chamber B in the form of a front cylinder washer E which also serves as a guide for an anvil block F adapted to act against a working implement Gr guided by a front head H at the forward end of the cylinder. On the rearward end of the cylinder A is seated a plated which in turn serves as a seat for a back head K. V I

' The parts comprising the casing of the tool, such as the cylinder A, the front head H, the plate J and the back head K may be secured relatively to each other in any suitable manner, as for instance, by the usual side bolts (not shown).

In accordance with the present invention the piston chamber B is provided with a piston L comprising in this instance a stem O slidable in the reduced bore D of the piston Serial No. 381,504.

chamber and a head 1? slidable in the enlarged bore O of the piston chamber B. On the rearward end of the stem 0 is a pressure surface Q constantly exposed to pressure fluid tending to actuate the piston L forwardly against the anvil block F and at the forward end of the headP is an actuating sur-' face R against which pressure fluid may intermittently act for returning the piston. An end surface S on the rearward end of the head P is constantly exposed to atmospheric pressure through a vent T leading from the rearward end of the enlarged bore C of the piston chamber to the atmosphere.

In the back head K is disposed a throttle valve U having a central chamber V which may be in constant communication with a source of pressure fluid supply, and in the side of the throttle valve U is a port W adapted to register with a passage X in the back head and communicating with a passage Y in the plate J and opening into the rearward end of the piston chamber B.

In the construction shown the piston chamberB is provided with a free exhaust port Z which is so located that a portion of the fluid from only the front endof the piston chamber B will be exhausted theret-hrough to the atmosphere.

In the present instance the stem 0 of the piston L also serves to control an initial admission of pressure fluid to the front end of the piston chamber B through an inlet passage b which leads to the front end of the enlarged bore O of the piston chamber and communicates with the reduced bore D at a point near the forward end thereof through a. port a. The port 0 is preferably so arranged that it will be uncovered by the stem O of the piston at about the time the piston delivers its blow against the anvil block F.

Additional means are provided for continuing the supply of pressure fluid to the front end of the piston chamber B after the port 0 has again been covered by the piston L on the return stroke of the piston. To this end the plate J is provided with a valve chamber d to accommodate a differential valve 6 comprising a head f and a stem g. 'The portion of the valve chamber wherein the stem 9 of supplv of pressure'fluid to the front end of Figure 1. pressure fluid fiowin'gfromthe to move the valve '6 into its closed position.

thevalve is adapted to slide opens directly into the rearward end of the reduced bore D of the piston chamber so that an actuating surface it on the end of the stem 9 will be constantly. exposedto pressure fluid tending On the free extremity of the head f of the valve is an actuating surface j of greater area than the actuating surface It and said actuating-surface 'j is exposed to pressure fluid" flowing'through the inlet passage 12 which, as

will be observed, communicates with. the enlarged portion of the valve chamber cl for moving the valve 6 into the closed position.

As may be readily observed from the foregoing description. the period of time which elapses between the opening of the port a and 'its'vclosing by the piston L is of short durationso that herefore an insuificient amount .1 of pressure fluid would-be suppl ed to the front end of the piston chamber. B to fully retract thex piston- L a ainstfthe' opposing pressure acting against the. pressure surface Q). In order therefore: to insure anample the piston chamber for returninn'the piston. the tool is prov ded with a supply passage is which leadsfrom a point near the rearward end of the reduced bore D of the piston chamber to the rearward end of the valve chamber (Z. so that in the open position of the valve pressure fluid mav flow directlv from the rearward end of the p ston chamber and through the corresponding end of the valve chamber (Z into the inlet passage b.- Communication between the supplv passage and the inlet passage 6 i s'in this instance controlled by the head 7; of the valve. the arrangement beinq such that the actuating surface 7' will seat directlv-over the inlet opening of the inlet passageb: a 7

As has been previously intimated. only a portion of the pressure fluid'utilized for actuating the piston L rearwardly is exhausted to the atmosphere through the exi cation between the exhaust passage 0 and an atmosphericport q in the closed position of the valve 6. I 7 a v The operation of. the device is as follows With the parts in the positionillustrated' in throttle valve U through the passages X and Y will enter the rearward end of the piston chamber B to act against the pressure surface Q, for driving the piston L forwardly againstthe anvil block F. Pressure fluid communication between the supply passage hand the inlet passage, Z2. 1 In this position of l the valve communication will be established between the exhaust passage 0 and the atmospheric vent q so thatthe air in the front I end of the piston chamber will be expelled to implement through the medium of the anvil block F. 7 i

As the piston L approachesathe forward limiting position of its travel the, stem- 0 of the pistonwill uncover the port 0 and pressure fluid will then flow into the inlet passage 6 to the front end of thepiston chamber to immediately start the piston L on its return stroke. At the same time pressure fluidwill flow to' the rearward end of the valve chamber cl to act against the 'actuating'surface In this way the valve 6 will be moved into the open position illustrated in Figure 2 and pressure fluid will then flow from the re-' surface i to such a value that the pressure acting against the actuating surface it of the V valve will predominate, it being understood of course that in this same position of the piston L the supply passage. 7: willhave been closed by the stem 'O of the piston. The valve 6 will then be moved to the closed position so that the frontend of thepiston chamher will be open to the atmosphere through the exhaust passage 0,-the' valve chamber (Z and the atmospheric vent T Throughout the operation of the tool the end surface S of the piston head P will be constantly exposed to atmospheric pressure through the vent T and only'pressures acting against the pressure surfaces Q, and R will be instrumental in actuating the piston L.

The present invention has been found to be unusually efficient in the matter of pressure fluid consumption. It iscapable .of'operating at an extremely high rate of speed and also of delivering aheavy hlow'to the working implement. This is due largely to the facts that the pressure fluid utilized for actuating the piston forwardly on its working stroke acts only expansively and that only the pressure fluid used for impelling the piston in one Cil direction is exhausted from the piston chamber, and to the further fact that during the forward stroke of the piston L the space for wardly of the pressure surface R is completely vented so that the forward movement of the piston L is in no wise opposed. Another feature of the present invention and one which is particularly desirable in hand held percussive tools is the absence of vibration or shock during the return movement of the piston. This is due to the small diflerential between the pressure surfaces Q and B so that the pressure for actuating the piston L rearwardly need be only slightly greater than that opposing the rearward movement of the piston.

We claim:

7 1. A fluid actuated percussive tool, comprising a cylinder having an enlarged bore and a smaller bore to form a piston chamber, a piston in the piston chamber having a head and a stem, a pressure surface on the stem constantly exposed to pressure fluid for driving the piston forwardly, a pressure surface on the front end of the head intermittently exposed to pressure fluid for returning the piston, a valve chamber, a valve in the valve chamber having diflerential actuating surfaces, the smaller of which is constantly exposed to pressure fluid tending to close the valve and the actuating surface of larger area being intermittently exposed to pressure fluid for opening the valve, a supply passageleading from the smaller bore to the valve chamber and controlled by the stem, an inlet passage leading from the valve chamber to the front end of the enlarged bore and communieating with the supply passage in the open position of the valve, a port affording communication between the smaller bore and the inlet passage and controlled by the stem to expose the last said pressure surface to pressure fluid for starting the piston on its return stroke and to simultaneously open the valve, thus permitting the flow of pressure fluid from the smaller bore through the supply passage and the inlet passage into the front end of the enlarged bore to complete the rearward stroke of the piston, an exhaust port in the cylinder to exhaust a portion of the fluid from the front end of the piston chamber, and an exhaust passage in the cylinder controlled by the valve for completing the exhaust of fluid from the same end of the piston chamber.

2. A fluid actuated percussive tool, comprising a cylinder having a piston chamber, a differential piston in the piston chamber having only two end pressure surfaces, one of said surfaces being constantly exposed to pressure fluid for driving the piston forwardly and the other surface being intermittently exposed to pressure fluid for driving the piston rearwardly, a surface on the piston intermediate the pressure surfaces and constant ly exposed to atmospheric pressure, a valve chamber, a valve therein constantly exposed to pressure fluid in the piston chamber tending to close the valve, an inlet passage in the cylinder controlled by the piston 'to intermittently expose the valve to pressure fluid for opening the valve, and supplying pressure fluid through the inlet passage independently of the valve to the front end of the piston for starting said piston on its return stroke, a supply passage controlled by the piston leading from theh rear end of the piston chamber to the valve chamber and communicating with the inlet passage in the open position of the valve, thus permitting the flow of pressure ing from the rear end of the piston chamber to the front end thereof to complete the rearward stroke of the piston, and ports and passages in the cylinder controlled by the piston and the valve for exhausting fluid alternately from only the front end of the piston chamher.

In testimony whereof we have signed this specification.

\VILLIAM A. SMITH, SR. IVILLIAM A. SMITH, JR. 

